> : > : You may not know the answer to this, but it's worth a shot. Wht kind of
> : > : accuracy can we expect using 'cheap' off-the-shelf GPS receivers?
> : >
> : > We're getting, with ntp4 on a 3.x kernel, about +- 4uSec with a cheap
> : > gps receiver + atomic clock on a i486 class machine.
> :
> : I've got the cheap gps receiver (Garmin 12XL), but what do you mean by
> : an 'atomic clock'? Should the GPS receiver's NMEA messages be adequate
> : enough to do the job? However, all I need is ms accuracy, so anything
> : below 500us is good enough for me.
>
> We have a cesium clock, which is generally called atomic clock, that
> we use for various things in our system. If the GPS gives out a PPS
> signal for the NMEA, then you can likely hit 1mS w/o any problems at
> all.
Cool. I was under the impression that the cheap NMEA signals only gave
2-5sec accuracy given the 2400 baud speed issues.
> Don't know a thing about the Garmin 12XL to know for sure about
> how it operates.
It just a standard 'cheap' GPS.
Nate
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